The Graft Infusion Technique (GIT) for Treatment of Peri-Implantitis Defects: Case Series

Peri-implantitis is a site-specific infectious disease that causes an inflammatory process in soft tissues, and bone loss around an osseointegrated implant in function. Several techniques with non‐surgical or surgical debridement and decontamination followed by ongoing supportive therapy or regeneration of the peri‐implant bone defects have been proposed in the literature. However, the literature is still unclear on an effective protocol for implant surface decontamination or the appropriate choice of regenerative materials. This case series describes a surgical technique to treat peri-implantitis osseous defects using a mixture of deproteinized bovine bone mineral with 10% porcine collagen (DBBM-C) in a block form, soaked in an appropriate antibiotic. The use of this combination provides advantages such as good graft adaptability along with localized antibiotic release without the use of systemic antibiotics. Thus, this technique might be an effective method to treat amenable peri-implantitis defects. Additionally, the proposed algorithm also allows for customized culture based antibiotic loading. To the best of the authors’ knowledge, this is the first case series documenting this technique for peri-implantitis defects. Long-term studies with controlled samples would be necessary for further evaluation.


Introduction
Peri-implantitis is an inflammatory process affecting the surrounding peri-implant tissues, which can result in loss of supporting bone structure [1]. The diagnostic criteria determines the prevalence of peri-implantitis, and has been shown to range from 6.6% [2], to 36.6% after an average of 8 years of implant loading [3][4][5].
With an increase in the number of implants being placed every year, there is a pressing need to develop an effective and predictable treatment for peri-implantitis.
The pathophysiology of peri-implantitis has been shown to have a more accelerated rate of progression compared to periodontitis [6], which is why a more aggressive treatment approach is often warranted [7].
The Sixth European Workshop on Periodontology concluded that non-surgical therapy alone appears to be insufficient in the treatment of most cases of peri-impla-ntitis and surgical therapy is usually necessary [7].
Various treatments involving non-surgical or surgical debridement and decontamination followed by ongoing supportive therapy [8][9], or regeneration of the peri-implant bone defect [9][10], application of antibiotics such as tetracycline to the implant surface [11][12], have been described in the available literature. However, the most effective protocol for implant surface decontamination and appropriate choice of regenerative materials is still unclear in the literature [13]. There have been several studies on surgical therapies, which have looked at the use of bone grafts / bone substitutes with and without membranes, and they have documented clinical and radiographic improvements for at least 3 years from the time of treatment [14][15][16][17]. The grafting materials, timing and surgical technique varied in the studies and it was difficult to determine the superior method [10]. Unfortunately, none of the available techniques have been established as being predictable in achieving successful clinical and radiograph outcomes in the long-term, and further research in relation to the regenerative treatment of peri-implantitis is warranted [10,13].
A mixture of deproteinized bovine bone mineral with porcine collagen in a block form (DBBM-C, Geistlich Bio-Oss® Collagen, Geistlich Pharma AG, Wolhusen, Switzerland) has been successfully used in the literature for ridge preservation and guided tissue regeneration with stable results [18][19]. However, there is only one reported study, which evaluated the use of this material for grafting peri-implantitis defects [20]. The present clinical case series seeks to evaluate the 5-6 month clinical and radiographic results of DBBM-C soaked in an antibiotic covered with a native bilayer resorbable collagen membrane (Geistlich Bio-Gide®, Geistlich Pharma AG, Wolhusen, Switzerland) for surgical regenerative therapy of peri-implantitis, using a single procedure approach.

Case Presentation 1
A 47-year-old non-smoker female patient with no significant medical history, presented to the dental office for evaluation of bone loss around implant #18. Tooth #18 was extracted at the referring dental office 5 years prior, due to endodontic failure and was grafted with freeze-dried bone allograft and collagen membrane. 5 months later, after confirming adequate radiographic bone fill, a 4.6x10.5mm external implant (BioHorizons, Birmingham, AL, USA) was placed as per manufacturer's recommendations using a 1-stage procedure and loaded with a definitive screw-retained restoration after 3 months. The patient was kept on a 6-month recall at the referring dental office. 5 years later, the patient was referred for evaluation of bone loss around #18 implant.
At the initial consultation appointment, a detailed periodontal exam was conducted. Her periodontal findings were normal with only isolated areas of mild gingival inflammation; however, #18 implant had deep probing depths of 6mm on the facial and lingual with spontaneous bleeding on probing but no suppuration ( Figure   1a). Medical history was non-contributory. Radiographic examination revealed a circumferential crater defect with bone loss up to 40% of the implant length ( Figure   1b, 8). The patient was diagnosed with moderate periimplantitis as per the Froum and Rosen [21] classification.
Following the initial consultation, a treatment plan involving non-surgical initial therapy, surgical intervention and three-month maintenance protocol was discussed and the patient consented for treatment. Initial therapy involved scaling and root planning using ultrasonic and hand scalers for the natural dentition and use of titanium hand curettes for implant #18 followed by oral hygiene instructions.  as reported in the literature [11][12]. The block was then shaped to conform to the defect shape, and the site was grafted with the block to fill the defect completely and the graft was covered with a native bilayer resorbable collagen membrane (Figure 7). The flap was closed such that it completely covered the graft and the membrane; it was sutured in place using 5-0 polyamide single interrupted sutures (Figure 8).
Pain control included using Ibuprofen 600 mg every 6-8 hours for days 1 and 2 and then as needed after that.
After the surgery, the patient was asked not to brush the surgical site for 7 days and use a soft brushing gently for the following 14 days. For the first week, the patient was prescribed 0.12% chlorhexidine mouthwash, which was to be used twice daily. The patient was seen at 1 week, 2 weeks, 3 weeks ( Figure 9) and 5 months after the  Her initial appointment was for a consultation and periodontal exam. Her periodontal findings were normal   (Figure 14a,b,c).
The site was grafted such that the block completely filled the defect (Figure 15a,b) and was covered with a native bilayer resorbable collagen membrane ( Figure   16). The flap was closed such that it completely covered the graft and the membrane and sutured in place using 5-0 polyamide single interrupted sutures ( Figure 17) and an immediate post-operative radiograph was taken to visualize the bone graft ( Figure 18). Pain control included using Ibuprofen 600 mg every 6-8 hours for days 1 and 2 and then as needed after that. After the surgery, the patient was asked not to brush the surgical site for 7 days and use a soft brushing gently for the folowing14 days. For the first week, patient was prescribed 0.12% chlorhexidine mouthwash, which was to be used twice daily.
Healing appeared to proceed uneventfully, and sutures were removed at 3 weeks. A periapical radiograph was taken at 6 months and it showed bone-fill in the grafted defect (Figure 20a shown to leave drug residues which might interfere with re-osseointegration and act as a reservoir of microorganisms [22]. In the GIT technique, the DBBM-C is soaked in an appropriate antibiotic (either sensitivity-specific antibiotic based on culture, or tetracycline [11][12], where culture is not possible). This may assist in providing localized antibiotic delivery, while using an osteoconductive carrier for future regeneration. A prior study evaluated the use of deproteinized bovine bone mineral in combination with tetracycline with beneficial effects [23].
However, this study also used systemic antibiotics, whereas the two cases in our study have been performed without systemic antibiotic loading. In cases with suppuration, the use of antibiotic sensitivity culture may provide an added benefit in selection of appropriate antibiotic The results cannot be extrapolated to serve as a general guideline for peri-implantitis. Compared to prior studies using particulate grafts, this technique is different in terms of using a shaped DBBM-C to fit around the defect snugly. Peri-implantitis defects have complex morphology, frequently with an intra-osseous component [25]. The graft used in this case series is easy to adapt and retain around such complex defects and is best suited for well-contained angular defects. This graft also provides good stability and volume maintenance, which are critical for regeneration. With advantages such as localized antibiotic release and good adaptability, the use of DBBM-C soaked in antibiotic may be an effective technique to treat peri-implant defects, using a